The present invention relates to position detection.
In a microfluidic device, channels may be formed in a substrate, and materials like gel, liquids or sample material may be transported through the channels. This can be accomplished, in the field of gel electrophoresis, by applying electric fields along the channels so that charged particles may be moved along the channels under the influence of an electric force.
In a fluid separation system of such a microfluidic device, different components which are separated, using electric fields or the like, may be detected optically. For this purpose, a light beam may be emitted onto a channel, so that molecules moving along the channel can be detected, for instance due to their fluorescence properties.
For microfluidic applications, particular requirements might have to be considered when determining and adjusting the detection position of an instrument. This holds for the transverse directions (like horizontal and vertical position relative to a chip structure, for instance a channel) and also for a longitudinal direction. Examples for such chip structures are applications related to flow-injection and component separation. It might be important or necessary, for a sufficient detection sensitivity, to be in conformity with accurate time and/or spatial distances relative to reference positions.
It may happen that the time dependence of a concentration ratio or an equilibrium state of used chemical agents, in the context of transport procedures using channels, correlates with a position on the chip or along a channel. For instance, for fluorescence detection with sample derivatization, it has to be considered during a measurement using a fluorescence label that the reaction time may be limited by effects like diffusion.
In the light of the small dimensions of microfluidic devices, even moderate requirements concerning relative positioning accuracy can correspond to very small absolute tolerances which, in many cases, are difficult to obtain or are obtainable only with high effort by sophisticated manufacturing procedures.
In many cases, measurement devices are used which enable to position a detector using an adjustment device before the measurement. However, such an adjustment may be complicated and time-consuming.